Re: [Xen-devel] Last GB of memory?

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

> Can anyone provide me an explanation as to why Xen refuses to access 
> the last GB of
> RAM as of late?  This machine has 6GB of memory, which I expect a 
> little under 4GB to
> be available to Xen for domains, however it's only allowing 3GB.  Same 
> thing
> with -testing and -unstable.
The e820 map shows that you have only 3GB RAM below the 4GB boundary. 
This is not uncommon -- it allows things like frame buffer and ACPI 
data to be mapped into low addresses without overlapping with any RAM 
(which would then be inaccessible and hence wasted).
Until we get PAE working properly, you are limited to 3GB on that 
system.
 -- Keir

>  (XEN) WARNING: Only the first 4GB of the physical memory map can be 
> accessed
> (XEN)          by Xen in 32-bit mode. Truncating the memory map...
> (XEN) Physical RAM map:
> (XEN)  0000000000000000 - 000000000009b800 (usable)
> (XEN)  000000000009b800 - 00000000000a0000 (reserved)
> (XEN)  00000000000e4000 - 0000000000100000 (reserved)
> (XEN)  0000000000100000 - 00000000bff70000 (usable)
> (XEN)  00000000bff70000 - 00000000bff78000 (ACPI data)
> (XEN)  00000000bff78000 - 00000000bff80000 (ACPI NVS)
> (XEN)  00000000bff80000 - 00000000c0000000 (reserved)
> (XEN)  00000000e0000000 - 00000000f0000000 (reserved)
> (XEN)  00000000fec00000 - 00000000fec10000 (reserved)
> (XEN)  00000000fee00000 - 00000000fee01000 (reserved)
> (XEN)  00000000ff800000 - 00000000ffc00000 (reserved)
> (XEN)  00000000fffffc00 - 0000000100000000 (reserved)
> (XEN) System RAM: 3071MB (3144748kB) <---- *???*
> (XEN) Xen heap: 10MB (10704kB)
>
> # xm info
> memory                 : 3071  <---- *???*
>
> I don't recall it doing this until recently.   Is this a fact of life 
> until PAE, or
> is this a bug relating to the fixes for the domain.c BUG I reported 
> earlier that Keir
> fixed?
>
> Thanks,
> -Chris
>
>
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